Humphrys, Tennant and Dykes

The company was founded in 1852 by Edward Humphrys, formerly chief engineer of Woolwich Dockyard, where Dykes was also employed in the steam factory.

It specialised in building large marine steam engines and boilers, including those for the Navy's fast cruisers and iron-clad battleships.

The 50 years of production started in the early days of screw-propellers (as opposed to paddle wheels) and spanned great changes in the available pressure from boilers and the resulting power of the engines, as well as in the construction and form of ships.

Although rated as 400 nominal horsepower, with 24 psi steam (reflecting the very low marine boiler pressures typical at that time) the engine had shown 1834 ihp.

At the 1862 International Exhibition Humphrys, Tennant and Dykes showed details of the 4-cylinder expansion engines for the Peninsular & Oriental Steam Navigation Company's ship Mooltan.

The same type of engine was also fitted to the Peninsular & Oriental Steam Navigation ship SS Carnatic, on which it had recorded 2442 indicated horsepower.

Even though these engines were operated with only 20–25 psi steam pressure, the compound system was claimed to give significant benefits in economy.

Power plants were also provided for vessels built for the overseas market, such as the Shikishima which was completed in 1899, with its sea trials indicating 15,000 horsepower from her twin triple-expansion engines.

A prestigious contract for Humphrys, Tennant and Co. was the power plant for the 1899 Royal Yacht Victoria and Albert (see image).

This engine layout with triple expansion via four cylinders was clearly successful and was fitted into a range of ships, including the four Drake-class cruisers of 1901, which with 43 Belleville boilers produced 30,000 ihp and 23 knots.